Two Linked Combo Boxes

I have an unbound form that displays timesheet summary and detail data in two
subforms. Each is linked to an unbound textbox on the main form. There are
two unbouund combo boxes, cboStaffID and cboPeriod, from which the user
selects the staff member and period to be displayed.

It's possible that when a new staff member is chosen, a record does not
exist for the currently selected date, and vice versa. If it doesn't, I want
to select the first item in the list. The following code works but seems
cludgy. Does anyone have a better idea?

' cboStaffID AfterUpdate code

Dim blnPeriodExists As Boolean
Dim dtePeriod As Date
Dim i As Integer

'Initialize blnPeriodExists, dtePeriod
blnPeriodExists = False
dtePeriod = Me![cboPeriod]

With Me![cboPeriod]

' Show timesheet periods for chosen staff member
.Requery

' If the date doesn't exist for this staff member, select the first
one in the list
For i = 0 To .ListCount - 1
If .ItemData(i) = dtePeriod Then
blnPeriodExists = True
Exit For
End If
Next i

If blnPeriodExists = False Then
.Value = .ItemData(0)
End If

End With

' Assign link for subforms
Me![txtTSID] = fintGetTSID(cboStaffID, cboPeriod)

Thank you.
Sprinks